JOINTS & MOVEMENTS JOINTS & MOVEMENTS By DR.SANAA ALSHAARAWY.
Quantitative shape analysis of intertesseral joints in tessellated … · 2019. 12. 22. · MPIKG...
Transcript of Quantitative shape analysis of intertesseral joints in tessellated … · 2019. 12. 22. · MPIKG...
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Quantitative shape analysis of intertesseral joints in tessellated calcified cartilage of sharks and rays (elasmobranchs)
Ronald Seidel1, Ahmed Hosny2, David Knötel3, Peter Fratzl1, Daniel Baum3, James Weaver2, Mason N. Dean1
1 Max Planck Inst., Germany; 2 Wyss Inst., USA; 3 Zuse Inst., Germany
Semi-automatic tiling recognition of tesserae networks
Companion/Future studies
Mesh-based quantitative analysis of intertesseral joints
Introduction: Sharks & rays have armored skeletons, comprised of uncalcified cartilage covered by mineralised tiles (tesserae). The mechanical function of this skeletal tessellation remains unclear. We used high-resolution imaging and developed advanced 3D data processing tools to characterize how tesserae interact at ultrastructural levels, gaining insight into form-function relationships of their complex joints and their roles in whole skeletal element performance.
1 mm
50 µm
Dorsal photo Ventral microCT
Tesserae
Jaws
Shark & ray tessellated cartilage
Acknowledgements: We thank Aravind Jayasankar & Jacob Naumann for providing images and colleagues at the MPI for fruitful discussion on these topics. A Human Frontier Science Program Young Investigator’s Grant (RGY0067) funded this work.
Round stingray: Urobatishalleri
Characterizing ultrastructural features of tesserae and intertesseral joints
A “best fit plane” bisects T1&2 joint space, allowing calculation
of intrusion, separation and flatness of tesseral edges.
Intertesseral fibrous zone
ITF
Intertesseral jointITJ
Intertesseral contact zone
ICZ
fb
Tesserae
Spokes
Interspoke region
Joint axis
Heterogenous grey value distribution (e.g. high values at edges, lower valuesin centers)
Binary segmentation separates tesserae from background
Individual tesserae separated by applying a hierarchical watershed segmentation to a 2D distance map
Tesserae network graph representation used to characterize 2D tilings of theskeletal element’s surface
Statistical information computed per tessera used to annotate an abstract graph representation of the tesserae network
initi al volume rendering
fo
reground segmentati on
nove
l segmentati on algorithm
grap
h vis
ualisati on & quanti fi cati on
2D surface ti ling
Surfaces cut to isolate relevant region and to reduce vertices and faces for faster computation
Joint region defined by a 30µm ROI enclosing opposing tesseral surfaces and the space between them
Neighboring tesserae (T1&2) segmented and their surface geometries described by a triangle mesh
T1&2 mesh regions in close proximity (≤2 µm) were identified as contact zones.
Remaining T1&2 mesh regions within the 30µm ROI were identified as fibrous zones
from 3D segmentati on
surface processing
defi ning joint areas
Size of tesserae
Num ber of neighbors
Surface curvature
Visualisation of tesseral morphometrics allows comprehensive 3D analyses of the organisation of tesseral networks to define underlying principles of form-function relationships in the tiling pattern.
SKELETAL ELEMENT & TESSERAE SHAPE ANALYSIS
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k 2k
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k 3k
3 4 5 6 7 8 9 10Number of neighbors
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erae
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We developed custom modules for semi-automatic tiling-recognition using AmiraZIB Edition to segment individual tiles in microCT scans of tesseral mats and quantify tesserae shape variation across skeletal elements in 3D.
TESSERAE SEGMENTATION PIPELINEWe developed an advanced shape-analysis-algorithm in Python to quantify tesserae interaction from microCT data by defining joint parameters, such as contact zones, joint flatness and interlocking. We present an exemplar data set; this technique will be applied to multiple joints in future work.
TESSERAE JOINT CHARACTERISATION PIPELINE
Intertesseral joints appear rather flat in 2D virtual vertical sections.
3D reconstructions of the com-plex joint arrangment of fibrous
attachment or contact zones.
spfb
2 µm
fb
T
100 µm
50 µm
spifz
ifzicz icz
Backscatter & Environmental Scanning Electron Microscopy
Polarized Light Microscopy TEM
Preliminary analyses of a tesseral neighbor-pair illustrate that, although the joint surfaces of tesserae have convoluted topographies (~0.6 flatness) with comparatively large intrusions into the joint space (up to 27µm), they are dominated by fibrous attachment areas (~86%), with only small regions (~14%) of neighbor contact including scant areas (~4%) of apparent interlocking. This suggests that in tessellated cartilage, unlike in other ‘tiled’ biological systems, interlocking plays little role in mechanics and the limited abutment of tesserae at contact zones may offer adequate skeletal stiffness in compression. These hypotheses will be tested via modeling work described in our ‘Companion/Future Studies’.
FINDINGS
Interlocking area835.7 µm2 = 4,15 % of ICZ
Contact zone areaArea of T1: 19514 µm2
Area of T2: 20789 µm2
Ø: 20151 µm2
= 13,92 % of ITJ
Fiber attachment areaArea of T1: 120698 µm2
Area of T2: 128586 µm2
Ø: 124642 µm2 = 86,1 % of ITJ
Intertesseral joint areaArea of T1: 140184 µm2
Area of T2: 149346 µm2
Ø: 144765 µm2
Joint flatnessFlatness of T1: 0.6
Flatness of T2: 0.57Ø: 0.59
QUANTIFICATION OF TESSERAE INTERACTION
Intrusion Ø intrusion: 7.2 µm
Max. intrusion: 27 µm= 41 % of BFP
SeparationØ distance: 19.3 µmMax. distance: 64,1 µm= 23.3 % of BFP
D O W N L O A D PUBLICATION
DEFINING JOINT SYMMETRY VIA THE BEST FIT PLANE ‘BFP’Sy
mmetry best fi t plane
Red grid cells indicate intrusion (where the meshes breach the BFP),
whereas blue grid cells indicate separation.
The ratio of BFP and ITJ areas describes joint flatness, with values
approaching 1.0 representing flatter surfaces)
3D prints enable testing of the degrees of freedom of intertesseral joints and...
...allow us to perform material testswith physical models of
bio-inspired tilings......the results of which can be verified by Finite Element Analyses of biomimicked tessellations(Jayasankar et al. 2017, inpress)
Tesserae
Perichondrium
Unmineralized cartilage core
Cross section of a skeletal element
25 µm
icz
ifz
itj
Vertical & planar section of tesserae
SR-microCT
fas = fiber attachment surface ics = intertesseral contact surface
Tesserae abut against one another forming contact zones, or are linked via unmineralized fibrous zones.
The collagenous joint fibers are firmly anchored in the mineralized matrix, forming flexible linkages.
SR-microCTics
ics
fas
fas
icsfas
20 µm
Knötel et al. 2017, inprep.
int
ertesseral contact zone
interte
sseral fi brous zone